Oracle doesn't need NetSuite's tech. It wants the company to increase its cloud-computing revenues. Ellison, the executive chairman, said in June that he thought that Oracle could slingshot its way into making $10 billion on cloud computing before its rival, Salesforce, hit that mark.

Salesforce is on track to do $8.3 billion in revenue in its current fiscal year, it says, and analysts expect it to hit $10 billion next year.

But that won't bring it to $10 billion before Salesforce CEO Marc Benioff. It clearly needs big acquisitions for that. NetSuite is expected to hit $1.2 billion in revenue in 2017, so that's a help.

And Oracle may not be done with big acquisitions. In June, the company sold $14 billion in bonds, so it still has a few billion from that debt sale to shop with, plus about $20 billion in cash.

Ellison's other company

Rumors that Oracle would eventually buy NetSuite have been circulating practically since NetSuite was launched in 1998.

NetSuite was the brainchild of Oracle cofounder Ellison, born in the same meeting that gave Benioff — who was an Oracle exec at the time — the idea for Salesforce.com.

NetSuite CEO Zach Nelson worked with Ellison, Benioff, and another key player, Evan Goldberg, at Oracle in the 1990s. Goldberg thought up the idea of software as a service, says Nelson. Goldberg wanted to do customer relationship-management software that helps salespeople track customers and leads, as a service over the internet.

Ellison said that the idea was interesting, but told Goldberg that the first step would be to build finance software, and then build customer software around that. Goldberg agreed to do that and Ellison funded his startup. The company was born as NetLedger. It would later change its name to NetSuite.

Ellison, through his venture funds, ultimately invested about $125 million and still owned just under 40% of the company.

Goldberg, still CTO and chairman of the board, owned an almost 3% stake in NetSuite. With the sale to Oracle, his stake is worth about $231 million.

Benioff said that he wanted to go build the CRM part, and Salesforce was born. Ellison offered seed money to fund that, too — about $2 million. But Ellison and Benioff began to feud almost immediately after that, as competition occurred between Oracle and Salesforce. And Benioff quickly kicked Ellison off Salesforce's board.

Ellison retained a lion's share of NetSuite of nearly 32 million shares. At $109 per share paid by Oracle, Ellison's portion is worth $3.48 billion.

While the rumor mill had also said that NetSuite could be a target by companies other than Oracle, Ellison's giant stake in the company makes that seem unlikely. He wouldn't want to sell it to a rival software company, for instance. And only a rival would spend $9 billion to buy it.

In this case, Oracle says that the deal to buy NetSuite will proceed if only 50% of the shares not owned by Ellison agree to take part in the acquisition. Oracle offered a 19% premium over Wednesday's closing-share price, so investors will likely be happy to sell.

Rock + hard place = acquisition

NetSuite has another reason to sell. Oracle had originally aimed its cloud software at large businesses leaving NetSuite's all-in-one cloud software geared toward smaller companies.

That's a rock and a hard place for Ellison. Either Oracle snuffs out NetSuite or NetSuite blocks Oracle.

This isn't the first time that Oracle has bought a company that Ellison had a partial ownership stake in.

In 2011, Oracle bought storage company Pillar Data Systems, in which Ellison had a majority stake. That deal did not involve any cash upfront. Pillar's owners were to be paid off by Oracle as they reached certain performance metrics.

Still, investors bristled and pension funds in Michigan and Pennsylvania sued Oracle over the deal. As part of the settlement, Ellison agreed to give up his share of the payout for Pillar, potentially worth nearly $575 million.

Investors have so far reacted with a "meh" to Oracle's huge $9 billion deal for NetSuite, one of the largest in Oracle's history. The stock is trading about flat.